The present invention relates to a method for measuring the control cross section area of a nozzle. The so-called Rota method, in which a flow passes through the nozzle in a supercritical ratio P.sub.A /P.sub.E =0.52 (for air), was previously used for such measurements. In so doing, a floating-body flow meter is arranged in front of or in back of the test sample, depending on whether vacuum or overpressure method is utilized. Such a method has the disadvantage that it is relatively time consuming and not particularly accurate, requires a greater quantity of models for every nozzle type, and is difficult to automate. It is further known to measure the mass flow e.g. by means of a caloric flow meter. In this case, the pressure and temperature of the in-flowing medium (that is, on the high-pressure side of the test sample) is additionally measured and kept constant in a corresponding manner. Such a measuring method is relatively complicated and slow.